The invention relates generally to pilot operated directional valves and, more particularly, to cartridge style proportional pilot operated directional valves that allow flow to be regulated proportionally to the pilot pressure.
Proportional pilot operated valves come in several different styles. These include surface mounted valves, so-called CETOP valves, and sectional valves. However, a cartridge style version of a proportional pilot operated valve has not been generally available. A cartridge style valve is advantageous in that it can be used in a single compact manifold together with many other valves to enable full hydraulic control of a machine. Furthermore, cartridge style valves tend to be more cost effective than the previously mentioned types.
In accordance with the foregoing, a novel valve is provided. In an embodiment of the invention, the valve has a sleeve with at least four sets of radial holes, and a spool disposed within the sleeve, with a channel being defined between the spool and the sleeve. The spool has at least two sets of radial holes, and the exterior surface of the spool has annular protrusions, each being in at least partial contact with the inner wall of the sleeve. When the valve is in an open position, the first set of radial holes of the sleeve is in communication with one of the two sets of radial holes of the spool, the second and third sets of radial holes of the sleeve are each in communication with the channel, and the fourth set of radial holes of the sleeve is in communication with the other of the two sets of radial holes of the spool. The spool may be kept in an open position by pressure from a flow of fluid that is provided at one end of the sleeve.
In an embodiment of the invention, the valve has a cap with an axial bore and a radial hole, in which an end of the sleeve is disposed inside the axial bore of the cap and is connected to the cap. The radial hole of the cap communicates with the axial bore of the cap, and a fluid path is defined from the radial hole of the cap, through the axial bore of the cap, and to the spool. Pressure from a fluid entering the radial hole of the cap may put the valve into the second open position, in which the first and second sets of radial holes of the sleeve are at least in partial communication with the channel, the third set of radial holes of the sleeve is at least in partial communication with one of the two sets of radial holes of the spool, and the fourth set of radial holes of the sleeve is in communication with the other of the two sets of radial holes of the spool.
An embodiment of the invention includes a means for biasing the spool into a neutral position, in which one or more of the annular protrusions of the spool blocks the first set and third sets of radial holes of the sleeve. In various embodiments of the invention, the biasing means is a spring.
During operation of an embodiment of the present invention, a first open position is provided by admitting a fluid through the second set of radial holes of the sleeve and through the channel to the third set of radial holes of the sleeve. The fluid is then allowed to exit the valve at the third set of radial holes of the sleeve and to pass to a hydraulic device. The fluid is further admitted from an outlet of the hydraulic device, through the first set of radial holes of the sleeve, and to the axial bore of the spool. The fluid is then passed through the axial bore of the spool, to the fourth set of radial holes of the sleeve, and allowed to exit the valve at the fourth set of radial holes of the sleeve.
A second open position of an embodiment of the present invention is provided by admitting a fluid through the second set of radial holes of the sleeve and through the channel to the first set of radial holes of the sleeve. The fluid is then allowed to exit the valve at the first set of radial holes of the sleeve and to pass to a hydraulic device. The fluid is further admitted from an outlet of the hydraulic device, through the third set of radial holes of the sleeve, to the axial bore of the spool. The fluid is then passed through the axial bore of the spool, to the fourth set of radial holes of the sleeve and allowed to exit the valve at the fourth set of radial holes of the sleeve.
Other features of the invention are described in, and will be apparent from the following description and the annexed drawings.